Съюзът е дума или група от думи,които свързват думи ,изрази или изречения .

Според начина на образуване биват:

-прости : and - u , but - но , or - или , after - след , because - защото , if - ако и др.

-съставни : in case - в случай че , as soon as

- веднага щом , either...or... - или ,neither...nor...-нито...нищо... и др.

Според употребата им съюзите биват :

- съчинителни - свързват думи,изрази или изречения
-подчинителни - въвеждат подчинени изречения.

Съчинителни съюзи са :

and - и

Betty and Tina are sisters .

but - но

This car is nice but expensive.

or - или

You can travel by bus or by train .

so - така че ; затова

It is hot,so I will open the window.

either...nor... - нито...нито..

These shoes are neither cheap nor comfortable .

while - докато

Dave was listening to the radio while his mother was cooking .

therefore - следователно , ето защо

The appointment isn't cancelled,therefore you must go.

besides - освен това

The hotel is full,besides you don't have a reservation .

still- все пак

She was determined to do it and still she was scared .

for - защото 

He told her,for he knew she would understand .

whereas - докато

Robert isn't the man we need whereas Henry has got the proper qualification .

or else - в противен случай

I have to finish the report until Sunday or else I will miss the deadline .

as well as - също ; както и

You should read as well as write in English .

as soon as - веднага щом

As soon as his parents left , Jimmy switched on the TV .

Подчинени съюзи са :

because - защото

I didn't go out because I was tired .

though/although - макар че ; въпреки че

Peter didn't come , though he had promised .

that - че

Andrew told me that Lilly had got married .

if/whether - дали

Philip asks if you will come to the party .

wherever - където и да

Wherever you go , don't forget you home .

as - тъй като ;както ; докато

We have to buy a map as we don't know the town .

since - откакто

I haven't seen her since she left the country .

whose - чийто

This is the man whose house was robbed .

until - докато

Please,wait here until Mr.Stevenson comes .

after - след като

Sheila started work after reading the newspaper .

before - преди да

Before you cross the street,always look both ways.

both..and.. - както.. така и 

Both Ally and Helen went to a disco .

despite/in spite of - въпреки ; независимо от

Despite what I said last night , I will help you .

Като съюзи се използват и причастия , местоимения и наречия .

Providing that he studies hard , he should pass the exam .
The man who lives next door is very nice .
This is the hotel where we stayed .